We investigated contemporary and historical influences on the pattern of genetic diversity of European roe deer (Capreolus capreolus). The study was conducted in northeastern Poland, a zone where vast areas of primeval forests are conserved and where the European roe deer was never driven to extinction. A total of 319 unique samples collected in three sampling areas were genotyped at 16 microsatellites and one fragment (610 bp) of mitochondrial DNA (mtDNA) control region. Genetic diversity was high, and a low degree of genetic differentiation among sampling areas was observed with both microsatellites and mtDNA. No evidence of genetic differentiation between roe deer inhabiting open fields and forested areas was found, indicating that the ability of the species to exploit these contrasting environments might be the result of its phenotypic plasticity. Half of the studied individuals carried an mtDNA haplotype that did not belong to C. capreolus, but to a related species that does not occur naturally in the area, the Siberian roe deer (C. pygargus). No differentiation between individuals with Siberian and European mtDNA haplotypes was detected at microsatellite loci. Introgression of mtDNA of Siberian roe deer into the genome of European roe deer has recently been detected in eastern Europe. Such introgression might be caused by human-mediated translocations of Siberian roe deer within the range of European roe deer or by natural hybridization between these species in the past.

Climate fluctuations during the Last Glacial Period between 115,000 and 11,500 years ago (Lokrantz & Sohlenius, 2006) played an important role in shaping the current species composition, distribution, and genetic diversity of mammals in Europe. During glaciations, the ranges of cold sensitive species were limited to refugial areas located in the Balkan, the Iberian and the Apennine Peninsulas (Hewitt, 2004;Taberlet et al., 1998) and south-eastern part of the continent (the Black Sea region and the Caucasus Mts.; Markova & Puzachenko, 2019). Contribution of a given refugium into postglacial recolonization processes varied a lot among species such as, for example, red deer Cervus elaphus (Niedziałkowska, Doan, et al., 2021), wild boar Sus scrofa (Niedziałkowska, Tarnowska, et al., 2021), or common vole Microtus arvalis (Stojak et al., 2015). Cold-adapted species such as, for example, reindeer Rangifer tarandus (Sommer et al., 2014), saiga antelope Saiga tatarica (Nadachowski et al., 2016), or arctic fox Alopex lagopus (Dalén et al., 2007), thrived in the glacial stages, expanded their ranges southward, and during the onset of interglacial they underwent massive, large-scale extinctions. Species of mammals that have very broad biogeographic niche (from the Mediterranean to the boreal zone) had more diverse response to geological time-scale pulsation of climate, most likely with several glacial refugia located at both lower and higher latitudes, where subpopulations diverged into different lineages and could have developed adaptations to different climate, habitat, and food-related conditions. Examples of such species include the bank vole Clethrionomys glareolus (Tarnowska et al.,

Glacial and interglacial periods throughout the Pleistocene have been substantial drivers of change in species distributions. Earlier analyses suggested that modern grey wolves (Canis lupus) trace their origin to a single Late Pleistocene Beringian population that expanded east and westwards, starting c. 25,000 years ago (ya). Here, we examined the demographic and phylogeographic histories of extant populations around the Bering Strait with wolves from two inland regions of the Russian Far East (RFE) and one coastal and two inland regions of North‐western North America (NNA), genotyped for 91,327 single nucleotide polymorphisms. Our results indicated that RFE and NNA wolves had a common ancestry until c. 34,400 ya, suggesting that these populations started to diverge before the previously proposed expansion out of Beringia. Coastal and inland NNA populations diverged c. 16,000 ya, concordant with the minimum proposed date for the ecological viability of the migration route along the Pacific Northwest coast. Demographic reconstructions for inland RFE and NNA populations reveal spatial and temporal synchrony, with large historical effective population sizes that declined throughout the Pleistocene, possibly reflecting the influence of broadscale climatic changes across continents. In contrast, coastal NNA wolves displayed a consistently lower effective population size than the inland populations. Differences between the demographic history of inland and coastal wolves may have been driven by multiple ecological factors, including historical gene flow patterns, natural landscape fragmentation, and more recent anthropogenic disturbance.